(CNA file photo)

Daytime highs in northern Taiwan are forecast at 25-26 degrees Celsius on Tuesday, down 5-6 degrees from a day earlier, according to forecaster Chang Cheng-chuan (張承傳).

Overnight temperatures are expected to drop to 24 degrees, he said.

Another wave of cold air is expected to move into the country over the weekend and remain until next Tuesday, during which time the mercury could fall as low as 20 degrees in northern Taiwan, he said.

The air quality around Taiwan, meanwhile, is expected to be good or fair throughout much of the country on Tuesday and Wednesday, except for Kaohsiung City and Pingtung County in southern Taiwan.

In those areas, the air was rated as fair as of 11 a.m. but was expected to worsen to "unhealthy for sensitive groups" later in the day and on Wednesday, with high PM2.5 and PM10 particulate concentrations.